What We Think We Know About CIRs/SIRs

We consider corotating interaction regions (CIRs) and their rapidly evolving counterparts, stream interaction regions (SIRs). Since we are looking ahead to the launch of PUNCH, which will observe the inner heliosphere in total and polarized white light, we use numerical MHD to create synthetic white-light images (polarized and total brightness and their ratio) of CIRs/SIRs emanating from idealized coronal holes. We compare the synthetic white-light images of CIRs/SIRs to STEREO heliospheric white-light images.